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PROLOG
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NAME
date — write the date and time
SYNOPSIS
date [−u] [+format]
date [−u] mmddhhmm[[cc]yy]
DESCRIPTION
The date utility shall write the date and time to standard output or attempt to set the system date and
time. By default, the current date and time shall be written. If an operand beginning with '+' is
specified, the output format of date shall be controlled by the conversion specifications and other text
in the operand.
OPTIONS
The date utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
Syntax Guidelines.
The following option shall be supported:
−u Perform operations as if the TZ environment variable was set to the string "UTC0", or its
equivalent historical value of "GMT0". Otherwise, date shall use the timezone indicated by the
TZ environment variable or the system default if that variable is unset or null.
OPERANDS
The following operands shall be supported:
+format When the format is specified, each conversion specifier shall be replaced in the standard
output by its corresponding value. All other characters shall be copied to the output without
change. The output shall always be terminated with a <newline>.
Conversion Specifications
%a Locale's abbreviated weekday name.
%A Locale's full weekday name.
%b Locale's abbreviated month name.
%B Locale's full month name.
%c Locale's appropriate date and time representation.
%C Century (a year divided by 100 and truncated to an integer) as a decimal number
[00,99].
%d Day of the month as a decimal number [01,31].
%D Date in the format mm/dd/yy.
%e Day of the month as a decimal number [1,31] in a two-digit field with leading <space>
character fill.
%h A synonym for %b.
%H Hour (24-hour clock) as a decimal number [00,23].
%I Hour (12-hour clock) as a decimal number [01,12].
%j Day of the year as a decimal number [001,366].
%m Month as a decimal number [01,12].
%M Minute as a decimal number [00,59].
%n A <newline>.
%p Locale's equivalent of either AM or PM.
%r 12-hour clock time [01,12] using the AM/PM notation; in the POSIX locale, this shall be
equivalent to %I:%M:%S %p.
%S Seconds as a decimal number [00,60].
%t A <tab>.
%T 24-hour clock time [00,23] in the format HH:MM:SS.
%u Weekday as a decimal number [1,7] (1=Monday).
%U Week of the year (Sunday as the first day of the week) as a decimal number [00,53]. All
days in a new year preceding the first Sunday shall be considered to be in week 0.
%V Week of the year (Monday as the first day of the week) as a decimal number [01,53]. If
the week containing January 1 has four or more days in the new year, then it shall be
considered week 1; otherwise, it shall be the last week of the previous year, and the
next week shall be week 1.
%w Weekday as a decimal number [0,6] (0=Sunday).
%W Week of the year (Monday as the first day of the week) as a decimal number [00,53]. All
days in a new year preceding the first Monday shall be considered to be in week 0.
%x Locale's appropriate date representation.
%X Locale's appropriate time representation.
%y Year within century [00,99].
%Y Year with century as a decimal number.
%Z Timezone name, or no characters if no timezone is determinable.
%% A <percent-sign> character.
See the Base Definitions volume of POSIX.1‐2008, Section 7.3.5, LC_TIME for the conversion
specifier values in the POSIX locale.
Modified Conversion Specifications
Some conversion specifiers can be modified by the E and O modifier characters to indicate a different
format or specification as specified in the LC_TIME locale description (see the Base Definitions volume
of POSIX.1‐2008, Section 7.3.5, LC_TIME). If the corresponding keyword (see era, era_year, era_d_fmt,
and alt_digits in the Base Definitions volume of POSIX.1‐2008, Section 7.3.5, LC_TIME) is not specified
or not supported for the current locale, the unmodified conversion specifier value shall be used.
%Ec Locale's alternative appropriate date and time representation.
%EC The name of the base year (period) in the locale's alternative representation.
%Ex Locale's alternative date representation.
%EX Locale's alternative time representation.
%Ey Offset from %EC (year only) in the locale's alternative representation.
%EY Full alternative year representation.
%Od Day of month using the locale's alternative numeric symbols.
%Oe Day of month using the locale's alternative numeric symbols.
%OH Hour (24-hour clock) using the locale's alternative numeric symbols.
%OI Hour (12-hour clock) using the locale's alternative numeric symbols.
%Om Month using the locale's alternative numeric symbols.
%OM Minutes using the locale's alternative numeric symbols.
%OS Seconds using the locale's alternative numeric symbols.
%Ou Weekday as a number in the locale's alternative representation (Monday = 1).
%OU Week number of the year (Sunday as the first day of the week) using the locale's alternative
numeric symbols.
%OV Week number of the year (Monday as the first day of the week, rules corresponding to %V), using
the locale's alternative numeric symbols.
%Ow Weekday as a number in the locale's alternative representation (Sunday = 0).
%OW Week number of the year (Monday as the first day of the week) using the locale's alternative
numeric symbols.
%Oy Year (offset from %C) in alternative representation.
mmddhhmm[[cc]yy]
Attempt to set the system date and time from the value given in the operand. This is only
possible if the user has appropriate privileges and the system permits the setting of the
system date and time. The first mm is the month (number); dd is the day (number); hh is the
hour (number, 24-hour system); the second mm is the minute (number); cc is the century and is
the first two digits of the year (this is optional); yy is the last two digits of the year and
is optional. If century is not specified, then values in the range [69,99] shall refer to years
1969 to 1999 inclusive, and values in the range [00,68] shall refer to years 2000 to 2068
inclusive. The current year is the default if yy is omitted.
Note: It is expected that in a future version of this standard the default century inferred
from a 2-digit year will change. (This would apply to all commands accepting a
2-digit year as input.)
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of date:
LANG Provide a default value for the internationalization variables that are unset or null. (See the
Base Definitions volume of POSIX.1‐2008, Section 8.2, Internationalization Variables for the
precedence of internationalization variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization
variables.
LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters
(for example, single-byte as opposed to multi-byte characters in arguments).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic
messages written to standard error.
LC_TIME Determine the format and contents of date and time strings written by date.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
TZ Determine the timezone in which the time and date are written, unless the −u option is
specified. If the TZ variable is unset or null and −u is not specified, an unspecified system
default timezone is used.
ASYNCHRONOUS EVENTS
Default.
STDOUT
When no formatting operand is specified, the output in the POSIX locale shall be equivalent to
specifying:
date "+%a %b %e %H:%M:%S %Z %Y"
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 The date was written successfully.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
Conversion specifiers are of unspecified format when not in the POSIX locale. Some of them can contain
<newline> characters in some locales, so it may be difficult to use the format shown in standard output
for parsing the output of date in those locales.
The range of values for %S extends from 0 to 60 seconds to accommodate the occasional leap second.
Although certain of the conversion specifiers in the POSIX locale (such as the name of the month) are
shown with initial capital letters, this need not be the case in other locales. Programs using these
fields may need to adjust the capitalization if the output is going to be used at the beginning of a
sentence.
The date string formatting capabilities are intended for use in Gregorian-style calendars, possibly with
a different starting year (or years). The %x and %c conversion specifications, however, are intended for
local representation; these may be based on a different, non-Gregorian calendar.
The %C conversion specification was introduced to allow a fallback for the %EC (alternative year format
base year); it can be viewed as the base of the current subdivision in the Gregorian calendar. The
century number is calculated as the year divided by 100 and truncated to an integer; it should not be
confused with the use of ordinal numbers for centuries (for example, ``twenty-first century''.) Both the
%Ey and %y can then be viewed as the offset from %EC and %C, respectively.
The E and O modifiers modify the traditional conversion specifiers, so that they can always be used, even
if the implementation (or the current locale) does not support the modifier.
The E modifier supports alternative date formats, such as the Japanese Emperor's Era, as long as these
are based on the Gregorian calendar system. Extending the E modifiers to other date elements may provide
an implementation-defined extension capable of supporting other calendar systems, especially in
combination with the O modifier.
The O modifier supports time and date formats using the locale's alternative numerical symbols, such as
Kanji or Hindi digits or ordinal number representation.
Non-European locales, whether they use Latin digits in computational items or not, often have local forms
of the digits for use in date formats. This is not totally unknown even in Europe; a variant of dates
uses Roman numerals for the months: the third day of September 1991 would be written as 3.IX.1991. In
Japan, Kanji digits are regularly used for dates; in Arabic-speaking countries, Hindi digits are used.
The %d, %e, %H, %I, %m, %S, %U, %w, %W, and %y conversion specifications always return the date and time
field in Latin digits (that is, 0 to 9). The %O modifier was introduced to support the use for display
purposes of non-Latin digits. In the LC_TIME category in localedef, the optional alt_digits keyword is
intended for this purpose. As an example, assume the following (partial) localedef source:
alt_digits "";"I";"II";"III";"IV";"V";"VI";"VII";"VIII" \
"IX";"X";"XI";"XII"
d_fmt "%e.%Om.%Y"
With the above date, the command:
date "+%x"
would yield 3.IX.1991. With the same d_fmt, but without the alt_digits, the command would yield 3.9.1991.
EXAMPLES
1. The following are input/output examples of date used at arbitrary times in the POSIX locale:
$ date
Tue Jun 26 09:58:10 PDT 1990
$ date "+DATE: %m/%d/%y%nTIME: %H:%M:%S"
DATE: 11/02/91
TIME: 13:36:16
$ date "+TIME: %r"
TIME: 01:36:32 PM
2. Examples for Denmark, where the default date and time format is %a %d %b %Y %T %Z:
$ LANG=da_DK.iso_8859−1 date
ons 02 okt 1991 15:03:32 CET
$ LANG=da_DK.iso_8859−1 \
date "+DATO: %A den %e. %B %Y%nKLOKKEN: %H:%M:%S"
DATO: onsdag den 2. oktober 1991
KLOKKEN: 15:03:56
3. Examples for Germany, where the default date and time format is %a %d.%h.%Y, %T %Z:
$ LANG=De_DE.88591 date
Mi 02.Okt.1991, 15:01:21 MEZ
$ LANG=De_DE.88591 date "+DATUM: %A, %d. %B %Y%nZEIT: %H:%M:%S"
DATUM: Mittwoch, 02. Oktober 1991
ZEIT: 15:02:02
4. Examples for France, where the default date and time format is %a %d %h %Y %Z %T:
$ LANG=Fr_FR.88591 date
Mer 02 oct 1991 MET 15:03:32
$ LANG=Fr_FR.88591 date "+JOUR: %A %d %B %Y%nHEURE: %H:%M:%S"
JOUR: Mercredi 02 octobre 1991
HEURE: 15:03:56
RATIONALE
Some of the new options for formatting are from the ISO C standard. The −u option was introduced to allow
portable access to Coordinated Universal Time (UTC). The string "GMT0" is allowed as an equivalent TZ
value to be compatible with all of the systems using the BSD implementation, where this option
originated.
The %e format conversion specification (adopted from System V) was added because the ISO C standard
conversion specifications did not provide any way to produce the historical default date output during
the first nine days of any month.
There are two varieties of day and week numbering supported (in addition to any others created with the
locale-dependent %E and %O modifier characters):
* The historical variety in which Sunday is the first day of the week and the weekdays preceding the
first Sunday of the year are considered week 0. These are represented by %w and %U. A variant of
this is %W, using Monday as the first day of the week, but still referring to week 0. This view of
the calendar was retained because so many historical applications depend on it and the ISO C standard
strftime() function, on which many date implementations are based, was defined in this way.
* The international standard, based on the ISO 8601:2004 standard where Monday is the first weekday and
the algorithm for the first week number is more complex: If the week (Monday to Sunday) containing
January 1 has four or more days in the new year, then it is week 1; otherwise, it is week 53 of the
previous year, and the next week is week 1. These are represented by the new conversion
specifications %u and %V, added as a result of international comments.
FUTURE DIRECTIONS
None.
SEE ALSO
The Base Definitions volume of POSIX.1‐2008, Section 7.3.5, LC_TIME, Chapter 8, Environment Variables,
Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2008, fprintf(), strftime()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event
of any discrepancy between this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .